1. Field of the Invention
The present invention relates generally to a viscous fluid drive device In particular, the present invention is concerned with an insulating retainer for mounting a bimetallic coil on a fan clutch.
2. Statement of the Related Art
A thermostatically-controlled viscous fluid clutch assembly for driving and rotating a vehicle cooling fan is well-known. A multi-bladed fan is removably secured to a body of the clutch. The fan and clutch assembly are installed between an accessory pulley (typically the water pump pulley) of a vehicle engine and a radiator. The clutch drives the fan at high speeds close to input speed when cooling is required and permits the fan to rotate at low speeds when cooling is not required. Thermostatic control of the fan through the clutch reduces airflow noise caused by fan rotation and the load on an engine, resulting in horsepower gain and improved fuel economy.
Bimetallic coils are often utilized to sense ambient air temperature in an engine compartment and engage or disengage the clutch. A coil expands and contracts in response to air temperatures and controls fluid flow inside the clutch in a well-known manner.
A conventional assembly method for a coil includes inserting a first end of the coil in a slot on the clutch housing and inserting a second end of the coil in a slot of a rotatable control shaft. Vibrations incurred by the clutch require an adhesive to secure and hold the first end of the coil on the cover. Due to the clutch's environment, a room-temperature vulcanizing (RTV) silicone is applied in the slot. While the RTV silicone holds the first end, various drawbacks exist, including a lengthy cure time and frequent maintenance and clogging of the tooling and nozzles used to apply the silicone.
The bimetallic coil is designed to control a cooling fan in response to air temperatures in the engine compartment. However, friction in a clutch can be great, and fluids for clutches are designed to operate for temperatures as high as 350.degree. F. The heated fluid contained in a clutch produces radiant heat which can affect the operation of the bimetallic coil.
The art continues to seek improvements. It is desirable to control clutch and fan rotation with a bimetallic coil. Additionally, it is desirable to eliminate costly RTV silicone for retaining a coil on a clutch. Coil operation can be improved if a coil can be insulted from radiant heat emanating from fluid contained in the clutch.